Section 4191. Keyway and Expansion Tubes
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Meet the following requirements:
1.���� Coated or uncoated sheets of 24 gage (nominal 0.6 mm thick) iron or steel formed to produce a trapezoidal offset in the face of the concrete of 1 inch (25 mm) plus 1/4 inch (6 mm) or minus 1/8 inch (3 mm).
2.���� Dimension and installation details as required in the contract documents.
3.���� Keyway punched along the center line of the face, to receive the bars.
4.���� Furnished in lengths which are multiples of the bar spacing.
5.���� Keyways formed on the grade during the paving operation may be of coated or uncoated sheets of 26 gage (nominal 0.4 mm thick) iron or steel.
B.��� Expansion Tubes to be used as Dowel Caps on Dowel Bars through Expansion Joints.
1.���� Noncollapsible metal or plastic tubes with one end closed.
2.���� Formed with a positive bar stop, capable of withstanding a push of more than 20 pounds (90 N).
3.���� The stop located at least 2 3/4 inches (70 mm) from the open end of the tube.
4.���� Internal diameter not more than 1/16 inch (2 mm) larger than the nominal diameter of the bar. That part of the tube having this diameter must extend beyond the stop a distance no less than the width of the expansion joint.